I then used the black sharpie pen to scribble a rough outline border, & drew on the wavy lines to guide my ink work.

How did I achieve that cool inky background?

Well.... I'd like to say it's some fancy pants technique, but the truth is I simply dipped my paintbrush into the Kaisermists and painted the wavy pattern on. Starting with the red first - because it's so dominant, then the turquoise, & finally with a finer tip brush, the denim ink. I also allowed each colour to completely dry before adding the next one.